Contact structure for electromagnetic actuator



.Dec. 29 195 9 E H. KUHN ETAL 2,919,327

CONTACT STRUCTURE FOR ELECTROMAGNETIC ACTUATOR 4 Sheets-Sheet 1 Filed May 20, 1957 m M Wm 3 Q m fil l L w D 7 a m 5 8 1, 6 U UMJ C b n m@ H H fl I. 7 6 5 m 41 H a a ,7 Z @fi /0 5 w M aw W'I-M ATTORNEYS Dec. 29, H. KUHN ET AL CONTACT STRUCTURE FOR ELECTROMAGNETIC ACTUATOR Filed May 20, 1957 4 Sheets-Sheet 2 i 5 7 mvemons ATTORNEY5 z #Hws Q W 4 Sheets-Sheet 3 I 3 a Z 5 4 L0 MAGNETIC ACTUATOR ATTORNEY5 1959 E. H. KUHN ET AL CONTACT STRUCTURE FOR ELECTRO Filed May 20, 1957 1959 E. H. KUHN ET AL 2,919,327

CONTACT STRUCTURE FOR ELECTROMAGNETIC ACTUATOR Filed May 20, 1957 4 Sheets-Sheet 4 ATTORNEYJ United States Patent CONTACT STRUCTURE FOR ELECTROMAGNETIC ACTUATOR Edward H. Kuhn, Whitefish Bay, and Lynn H. Matthias,

Fox Point, Wis., assignors to Allen-Bradley C0,, Mi:- waukee, vWis., a corporation of Wisconsin Application May 20, 1957, Serial No. 660,115

Claims. (Cl. 200-104) This invention relates to electrical switches. and it more specifically resides in a contact structure that has a set of stationary contacts and a movable bridging contact for movement into and away from engagement with said stationary contacts, in which structure the bridging contact may be arranged for normally closed contact operation or normally open contact operation; in one specific form of the invention the stationary contact members have spaced contact ends with a gap therebetween and one of the stationary contact members extends from its contact end upwardly and then horizontally over itself in a terminal end that spans across the gap between the members, so that connections with other circuit elements can be made for both members at one side of the contact structure, the portion of the extended stationary contact member spanning the gap between members may comprise spaced ribs that straddle a spring seat for a contact bias spring that urges a movable bridging contact toward contact engagement, the movable bridging contact being held for guided movement by a contact carrier that has an abutment spaced to strike and carry the movable bridging contact to contact open position for either normally open or normally closed operation of the'switch.

In electrical control circuits for motors, machine tools and similar applications where the switches employed must be readily adaptable for a variety of circuit conditions, it is most desirable to have contact structures that may be arranged for either normally open or normally closed operation without recourse to any substantial revision or rearrangement of the switch elements. It is further desirable to provide standardized switches that may be assembled with varying numbers of both normally open and normally closed contacts, to meet the demands of the multitude of circuit requirements which are fulfilled by such switches; -In the present invention a simple reversal of a movable contact, together with its bias spring, from one side of the stationary contacts to the other side accomplishes a change over from normally closed to normally open position, or normally open to normally closed position. Also, the switch structure provides for convenient addition of contacts to meet a variety of circuit arrangements.

It is an object of this invention to provide a switch having contacts that may readily be arranged for either normally open or normally closed operation, without any substitution or introduction of parts for either mode of operation.

It is another object of this invention to provide a switch in which terminals for connection to lead wires are conveniently arranged at the front of the switch structure.

It is another object of this invention to provide a switch having improved guiding for movable contacts.

It is another object of this invention to provide a switch adapted to serve as a relay in control circuit networks, in which individual arc chambers are provided for each set of contacts.

It is another object of this invention to provide a switch in which additional auxiliary contacts may be conveniently added to the structure.

It is another object of this invention to provide a switch to function as a relay for control circuits, in which hoods are provided for the contacts without objectionable increase in overall dimensions of the switch.

The foregoing and other objects and advantages of this invention will appear from the description to follow. In the description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration and not of limitation a particular form in which the invention maybe embodied.

In the drawings:

Fig. l is a front view in elevation of an electromagnetically operated switch embodying the invention, with parts of the switch being broken away and in section to show the contact structure within the contact hood,

Fig. 2 is a right side view in elevation of the switch in Fig. 1, with a portion thereof-being in section as viewed through the plane. 2 2 designated inFig; 1,

Fig. 3 is a plan view of the switch with a portion in section as .viewed through the plane -33 designated in Fig. 1,

Fig. 4 is a fragmentaryright sideview in elevation of the switch viewed in section on the plane 4-4 designated in Fig. 1,

Fig. 5 is a fragmentary left side view of the lower portion of the switch,

Fig. 6 is a view in perspective of contacts and terminals forming a part of the switch, ,in which the contacts are disposed for anormally open mode of operation, and

Fig. 7 is a viewin perspective of ,contacts and terminals forming a part of the switch, in which the contacts are disposed for anormally closedmode of operation.

Referring now to thedrawings, there is shown a vertical base plate .1 upon which is mounted an electromagnetic actuator 2 and a contact hood 3 overhanging the actuator 2. Forming the body ofthe electromagnetic actuatori2 is a coil housing 4-formedof a right-hand'half shell 5 and a left-handhalf shell 6 placed against one another to enclose an operating coil 7 thatisshowvn in dotted outline in .Fig. 2. .Suitable terminals 8 for the coil 7 extend from the front of ,thehousing 4. The two half shells 5, 6 are held .togethenby a set of four assembly bolts 9, and a mounting bolt 1,0 extends through'the housing .4.-from the front to rear from which it emerges with a threaded end in engagement with the base plate 1.

The portion of the coil housing 4 above the coil7 is channel-shaped, with the trough of the channel-like configuration running from side to side, as shown in Fig. 2. Received within the channel-like configuration of the housing 4 is an inverted U-shaped magnetic field piece 11 having downwardly extending legs overhanging the sides of the housing 4. The field piece 11 is retainedin position by the mounting bolt- 10, which extends through the field piece 11, as well asthehousing 4. A switch actuator 12 that has a stirrup shaped configuration, when viewed from the front as in Fig. 1, fits over the field piece 11 and is free to move upward from and downward to the lowermost position shown in Fig. 1. To guide the movement of the actuator 12, it is in slidable engagement with the coil housing 4.

This engagement occurs at the sides of the trough of the channel-like configuration at the top of the housing 4, and between the lower ends of the downwardly extending legs of .the actuator 12 and sides of the housing 4. The lower ends of the actuator 12 are also in an interlocked connection with the opposite ends of a magnetic armature 13 extending through the central opening of the coil 7. As the coil 7 is energized the armature 13 responds by an upward movement into engagement with the field piece 11, and the switch actuator 12 being interlocked with the armature 13 moves in unison therewith. The electromagnetic actuator 2, which has been briefly described herein, is more fully treated in Letters Patent No. 2,692,314, dated October 19, 1954, and entitled Electromagnetic Actuators.

The contact hood 3 is preferably molded as a unitary whole from an insulating material such as a phenolformaldehyde resin. It has a rear wall 14, seen in Figs. 2, 3 and 4, which abuts the upper face areas of the base plate 1, and from the back wall 14 there protrudes a pair of bosses 15, one of which is seen in Fig. 3, that extend into complementary openings in the base plate 1 for orientating the contact hood 3 in proper place. Extending forwardly from the back wall 14 is a roof 16 which is at a level somewhat beneath the upper edge of the wall 14, and dividing the upper face of the roof 16 into uniform areas is a set of rearwardly and forwardly extending vertical ribs 17. A pair of the ribs 17 are shaped to receive a pair of mounting bolts 18 that pass on a diagonal through the respective ribs 17 and through the back wall 14 to emerge for threaded engagement with the base plate 1, to thereby hold the contact hood 3 in place.

At the forward edge of the roof 16 there is a depending front wall 19 having an enlarged forwardly protruding lower lip 20 that extends across the front of the hood 3 to serve as a mounting abutment for a set of stationary contacts to be described. A set of vertical partition ribs 21 extend forwardly from the wall 19 and its lip 20 to subdivide the space to the immediate front, and each rib 21 is in alignment with one of the ribs 17 to form a continuation thereof. A pair of side walls 22 complete the exterior of the contact hood 3 to thereby provide a hood 3 closed at the front, back, sides and top and open at the bottom to receive movable contact structure to be described.

A series of vertical fore and aft extending partitions 23 divide the interior of the contact hood 3 into compartments, and the partitions 23 are in alignment and merge with the ribs 21 at the front of the hood 3. Each of the compartments, thus formed within the hood 3, provides a separate housing for a set of contacts or a pole of the switch. In this manner, individual arc chambers are provided for each contact set.

A set of front terminals 24 are fastened to the underside of the lip 20'by attachment screws 25. Each front terminal 24 has a front stationary contact 26 disposed within a chamber of the hood 3, in a position that is a short distance behind the front wall 19. Each front terminal 24 extends forwardly from its contact 26 outwardlv from the front of the lip 20 to present a turned connection end 27 that mounts a suitable terminal screw 28 for the purpose of making connection with a lead wlre forming a part of a circuit network of which the switch is to be a part. Each front terminal 24 may be pos tioned with the contact 26 and connection end 27 facing downwardly, as shown in Figs. 2 and 6, in which instance it is arranged for a normally open contact arrangement. Each front terminal 24 may be secured to the lip 20 in the alternative position shown in Figs. 4 and 7, which is inverted from the position of Figs. 2 and 6. This inverted position places both the front statlonary contact 26 and the connection end 27 upwardly for a normally closed contact arrangement. The position of the connection end 27 indicates whether the associated contact 26 is arranged for a normally open or normally closed mode of operation, and simple visual inspection of the connection end 27 eliminates any necessity for inspection within the contact hood 3 for determining the contact arrangement.

For each front terminal 24 there is a corresponding rear terminal 29 directly to the rear. Each terminal 29 is of a complex configuration, as clearly shown in perspective in Figs. 6 and 7, and has a pair of rear stationary contacts 30 placed one above and one below a contact mounting tab 61 at the lower rear of the terminal. The lower contact 30 serves for a normally open mode of operation and the upwardly facing contact 30 serves for a normally closed mode of operation. Adjacent the rear contacts 30 of a rear terminal 29 is a mounting seat 31 having a threaded opening. Each rear terminal 29 extends upwardly from its seat 31 in the form of a pair of spaced ribs 32. After a short vertical extent, the ribs 32 have a forwardly inclined rise and then a forwardly extending run to merge with a connection end 33. The connection end 33 is disposed vertically, and a pair of toes 34 extend forwardly from each side of the base of the connection end 33. To lend strength to the ribs 32 of each rear terminal 29, a reinforcing 35 extends crosswise between the ribs 32 in a position above and slightly forward of the contacts 30.

Each rear terminal 29 is held in position within the contact hood 3 by means of an attachment screw 36 that extends through a pilaster 37 standing out from the back wall 14 of the hood 3. The bottom end of each attachment screw 36 is in threaded engagement with the mounting seat 31 of the associated terminal 29 and is drawn up tight to mount the seat 31 firmly against the bottom face of the pilaster 37. The toes 34, at the forward end of each terminal 29, rest upon a ledge 38 formed as a part of the front wall 19, as is shown in Figs. 2 and 4. Each connection end 33 extends outwardly through an opening 39 in the roof 16 of the hood 3 and projects upwardly from the roof 16. The ribs 32 are received in complementary grooves 40 on the underside of the roof 16, as shown in Fig. 1, with the upper sides of the ribs 32 being closely adjacent the underside of the roof 16. With each attachment screw 36 drawing the associated mounting seat 31 firmly against the underside of the associated pilaster 37, and the forward end of each terminal 29 being held in place by both the toes 34 resting upon a ledge 38 and the upper sides of the ribs 32 being closely adjacent the underside of the roof 16, each terminal 29 is firmly and securely held in place. Completing each terminal 29 is a terminal screw 41 threadedly received in the exposed connection end 33, which provides for connecting to lead wires of a circuit network.

The ribs 32 of each rear terminal 29 are spaced laterally from one another to straddle a spring seat 42 formed in the underside of the roof 16 at a point medially between the associated front stationary contact 26 and rear stationary contacts 30. Each spring seat 42 includes an inverted frusto-conical central boss 43 about which an end of a spring may be placed, as shown in Figs. 1 and 4, when the associated contacts are arranged for a normally closed mode of operation.

A cross bar 44 forms the top of the switch'actuator 12. A group of integrally molded channel-shaped electrical barriers 45 are disposed along the upper face of the cross bar 44 with the channel of each barrier 45 directly below the lower end of a partition 23 of the contact hood 3. The barriers 45 function to form orientating seats for a set of movable contact carriers 46. Each carrier 46 is a stamping of generally U-shaped configuration, as seen from the front, that is positioned between two adjacent barriers 45, and is attached by a mounting screw 47 received in the cross bar 44. Each carrier 46 has a pair of downwardly extending projections 48 that are received within complementary grooves molded in the cross bar 44. In this manner each movable contact carrier 46 is firmly secured in a manner precluding turning or twisting out of position.

Each vertical side of each U-shaped carrier 46 is formed as two spaced rising guide rails 49, with the upper end of each guide rail 49 being slightly tapered and bent outwardly to facilitate assembly. Extending horizontally between the two rails 49 of a side is a cross member 50 that is disposed at a level approximately twothirds the height of the rails 49. The members 50 of a carrier .6 are at dilferent levels, as particularly shown in ig. l, for a purpose to be described, and the carriers 46 are preferably of a case hardened steel to reduce wear and to eliminate fragmentary separation of particles that might cause, switch failure.

A movable bridging contact 51 is carried by each movable contact carrier 46, which spans the gap between the associated front stationary contact 26 and rear stationary contact 30 with which it is to be engaged. The contacts 51 are preferably case hardened, like the carriers 46, to withstand wear.

Each movable bridging contact 51 has a dished appearance, as seen from the side, and mounts contacts 55 at its ends which are in alignment with the stationary contacts 26, 50 for engagement therewith. A central portion 52 of each bridging contact 51 has short side wings 53 that are inserted between the spaced guide rails of the contact carrier 46 and a contact bias spring 54 is seated against the side of the central portion 52 which forms the center of the dished area. The spring 54 is connected to the bridging contact 51 by insertion of an end through an opening 62 in the central portion 52, which end is turned to lay over the contact whereby each bridging contact 51 and its associated spring 54 may be treated as an assembly.

Each movable bridging contact 51 is carried by the movable contact carrier 46 in one of two alternative positions, depending upon whether the contacts are to be employed for normally open or normally closed operation.

For a normally open contact arrangement, as shown in Fig. 2, at the far right in Figs. 1 and 3 and in Fig. 6, the movable bridging contact 51 is disposed with the bias spring 54 to the underside and each side wing 53 inserted between a pair of guide rails 49 at a level beneath an associated cross member 50. The bias spring 54 is compressed between the central portion 52 of the movable bridging contact 51 and the horizontal bottom of the movable contact carrier 46, with the lower end of the bias spring 54 encircling the head of the associated mounting screw 47 to be retained in position. The fit between each bridging contact 51 and the four associated guide rails 49 is of comparatively small clearance, so that each side wing 53 is restricted from forward and backward movement and the adjacent side edges of the central portion 52 are restricted from side-' ward movement. The guide rails 49 of each contact carrier 46 thus form a track that permits upward and downward movement of the associated movable contact 51, but in which sideward or end to end movement of the bridging contact 51 is restricted.

For the normally open contact arrangement, as above described, the bias spring 54 urges the movable bridging contact 51 upwardly against the underside of the cross members 50, when the electromagnetic actuator 2 is deenergized and the armature 13 is in the lower position shown in Figs. 1 and 2. For this deenergized position the contacts 55 of the movable bridging contact 51 will be spaced beneath the stationary contacts 26, 3t) and hence, in an open circuit position. Since one cross member 50 is slightly elevated above the other the contacts 55 will be on a slight incline. When the electromagnetic actuator is now energized the armature 13 and the switch actuator 12 are moved upwardly. The movable contacts 56 of the movable bridging contact 51 will strike the stationary contacts 26, 30 and come to rest before the actuator 12 completes its upward stroke. As the actuator 12 continues to move upwardly, after the contacts 56 engage the contacts 26, 30 the cross members 50 will rise above-the wings 53 and there will be an additional compression of the spring 54, thereby establishing contact pressure for the closed contact position. As the cross members 50 rise from the wings 53 the contacts 55 will roll from their inclined position to a horizontal position. Thewipe that thereby occurs between stationary and movable contacts aids to keep the contacts clean.

When the electromagnetic actuator 2 is deenergized the armature 13 and switch actuator 12 fall. The cross members of the movable contact carrier 46 will likewise descend and strike the side wings 53 of the movable bridging contact 51. The contacts 56 will then be abruptly moved downwardly and out of engagement with the contacts 26, 30 to achieve quick contact separation.

For a normally closed contact arrangement, the movable bridging contact 51 is inverted and disposed above the stationary contacts 26, 30, as shown in the chamber second from the right in Figs. 1 and 3, and in Figs. 4 and 7. In this position the upper end of the bias spring 54 is received by the associated spring seat 42 and encircles the boss 43. The spring 54 thus urges the movable bridging contact 51 downwardly. The wings 53 of the movable bridging contact 51 are again inserted between the rails 49 of the movable contact carrier 46 for guided vertical movement, but, in this instance, they are disposed above the cross members 50. With the electromagnetic actuator 2 deenergized and the armature in its lower position of Figs. 1 and 2, the cross members 50 of the movable contact carrier 46 are at a level that permits the bias spring 54 to urge the movable bridging contact 51 downwardly until the contacts are in engagement with the stationary contacts 26, 30. This is the position shown in Figs. 1, 4 and 7. When the electromagnetic actuator 12' is now energized, so that the switch actuator 1'2 is moved upwardly in response to armature movement, the cross members 50 will strike the wings 53 of the movable bridging contact 51 from the underside and raise the movable bridging contact 51 with a quick contact separation. The cross members 50 will carry the movable bridging contact 51 into the circuit opening position shown in the dotted lines of Fig. 4. Upon subsequent deenergization of the electromagnetic actuator 2, the switch actuator 12 will fall and the movable bridging contact 51 will descend therewith. The bias spring 54 will ensure rapid descent of the bridging contact 51 in unison with the descent of the movable contact carrier 46, until the movable contacts 55 again contact the stationary contacts 26, 30. The spring 54 remains under compression at all times, so that contact pressure for closed contact condition will be substantial. Wiping action of the contacts is also had for normally closed operation by reason of the slight difference in level of the two cross members 50 of a carrier 46.

The construction, shown and described, provides a contact structure for a control relay in which each set of contacts, or contacts of a pole, are provided with an individual arc chamber for improved insulation between poles and for enhanced arc interruption upon contact separation. The contact structure also enhances the versatility of the relay by providing for either normally open or normally closed contacts with identical parts. All that is required is a simple inversion of the movable bridging contact 51 together with its bias spring 54 between a position below the stationary contacts 26, 30 and a position above the stationary contacts 26, 30. There is no need for supplementary parts or for the substitution of different parts to have one mode of operation or the other mode.

Where both normally open and normally closed contacts are employed in a single switch it is sometimes desirable to have the normally open contacts close before the other open, and in other applications it is desirable to have the normally closed contacts open in advance of the closing of the normally open contacts. The bridging contacts 51 may be of thin material and by selecting a depth of the dish for the mid portion 52, the desired sequence of contact operation may be had, thus increasing the versatility of the apparatus.

The invention further provides movable contacts that are held and guided by four spaced guide rails that ensure alignment of the movable contacts with the stationary contacts. The guiding gives an enhanced stability to the movable contacts. Further, the connection ends 27, 33 of the terminals 24, 49 are all disposed at the front of the contact hood 3. They are readily accessible and there is no need to reach to the rear of the hood structure to make connection with the terminals for the rear contacts. When the apparatus is placed in a cabinet, or other enclosure, connections may be made with ease.

The rear terminals 29 are formed in a manner that does not interfere with the spring seat 42 employed for the normally closed contact arrangement. Separated conductive ribs 32 straddle the spring seat 42 and extend above and across the gap between the front and rear stationary contacts. This straddle construction gives the dual advantage of terminal connections at the front of the structure and contacts readily reversible between the two positions, normally open and normally closed.

The contact hood 3 of the switch structure shown in the drawings houses four sets of contacts and, as such, the switch is termed a four-pole switch. It is readily understood that a contact hood for some other number of contacts sets, or poles, may be used. In addition, auxiliary contacts may be placed to the sides of the electromagnetic actuator 2, such as exemplified by the auxiliary contact structure 56 disposed at the left of the actuator 2, which is shown in Figs. 1, 3 and 5. For the auxiliary contact structure 56 a mounting plate 57 is attached to the base plate 1 by suitable mounting screws, not shown. An auxiliary contact hood 58, of molded insulating material, is mounted at its back to the plate 57 by means of nuts and bolts 59 and extends forwardly from the plate 57 to range alongside the switch actuator 12. The auxiliary contact hood 58 is similar to a single compartment of the contact hood 3, being closed on the sides, front, back and top, while open at the bottom. The configuration in the interior of the auxiliary hood 58 is nearly identical to that of a compartment of the hood 3. A front terminal 24 is mounted on the auxiliary hood 58 in like fashion as the terminals 24 for the contact hood 3 and a rear terminal 29 is secured to and mounted within the auxiliary contact hood 58 in like fashion as the rear terminals 29 for the contact hood 3.

A small bracket 60 is secured to the side of the switch actuator 12 and extends sidewardly to beneath the auxiliary contact hood 58. Bolted to the bracket 60 is another movable contact carrier 46, like the carriers 46 standing upwardly from the cross bar 44. A movable bridging contact 51 with an associated contact bias spring 54 is placed in the interior of the auxiliary contact hood 58 and is carried by the movable contact carrier 46 in similar fashion as in the instance of the contact assemblies for the contact hood 3. The movable bridging contact 51 for the auxiliary contact assembly 56 may, likewise, be placed for either normally open or normally closed operation and in Fig. the contact structure is shown in dotted lines in normally open contact arrangement. As the switch actuator 12 is moved upwardly and downwardly in response to energization and deenergization of the electromagnetic actuator 2, the bracket 60 will carry its associated movable contact carrier 46 so as to have a switch operation like that described in connection with the contact assemblies for the hood 3. If desired, a second auxiliary contact structure 56 may be mounted on the right-hand side of the electromagnetic actuator 2 to provide further switch contact assemblies if the need arises.

The invention provides a contact structure adapted for use in relays, and like switches, that may be constructed with any of a number of contacts sets, or poles, so as to fulfill a variety of circuit arrangements. In control circuits for automatic machine tools or other automatic or semiautomatic machines having extensive control circuits, the circuity involved may require a number 8 of similar relays but differing in the number of contact sets and as to normally open and normally closed contact arrangement. The contact structure described aids as a. fulfillment of such circuit requirements through a standard relay construction. Further, the contact structure places terminals for convenient wiring and insulates contact sets from one another by separate compartments for the sets.

We claim:

1. In an electrical switch the combination comprising a contact hood having a roof and sides, a pair of terminals with contact ends within said hood spaced from one another to present a gap therebetween, one of said terminals extending upwardly from its contact end to a position directly beneath the hood roof and hence over said gap and along the underside of said roof with a connection end to the side of the gap opposite its contact end, said connection end extending from the hood to project therefrom; a movable contact carrier with guide rail means extending parallel to the line of motion of the movable carrier and with stop means at a point intermediate the ends of the rail means; a movable bridging contact spanning said gap that is movable into and away from engagement with said terminal contact ends, which movable contact is engaged by said rail means and disposable above the stop means and disposable below the stop means; and a bias spring disposable between the movable contact and the hood roof and disposable between the movable contact and said contact carrier.

2. In an electrical switch the combination comprising a contact hood having a roof and sides, a pair of terminals with contact ends within said hood spaced from one another to present a gap therebetween, one of said terminals extending upwardly from its contact end to a position directly beneath the hood roof and hence over said gap and along the underside of said roof with a connection end to the side of the gap opposite its contact end, which connection end extends from the hood to project therefrom; a movable bridging contact spanning said gap that is movable into and away from engagement with said terminal contact ends which may be disposed beneath said terminal contact ends and which may be disposed above said terminal contact ends in which latter position it is beneath the terminal portion spanning the gap between terminal contact ends; and a bias spring for the movable contact which may be disposed below the movable contact and which may be inserted between the movable contact and said contact hood roof.

3. In an electrical switch the combination comprising a front terminal with a connection end and a contact end to the rear thereof; a rear terminal having a contact end spaced to the rear of the contact end of the front terminal to present a gap therebetween, and turning upwardly and then over the gap with a connection end to the front of the gap, the portion of the rear terminal extending over the gap comprising a pair of spaced conductive ribs; a first spring seat positioned between said ribs; a movable contact carrier with a second spring seat spaced beneath the first spring seat; a movable bridging contact carried by said carrier and spanning said gap that is movable into and away from engagement with the contact ends of said front and rear terminals, said bridging contact being disposable above the contact ends of said terminals and also being disposable beneath the contact ends of said terminals; and a bias spring urging said bridging contact toward engagement with the contact ends of said terminals, which bias spring is seated against said first spring seat when said bridging contact is disposed above said contact ends and is seated against the second spring seat when said bridging contact is disposed below said contact ends.

4 n an electrical switch the combination comprising a contact hood having a roof and sides; a front terminal with a connection end and a contact end to the rear thereof within said hood; a rear terminal having a contact end within said hood spaced to the rear of the contact end of the front terminal to present a gap therebetween, and turning upwardly toward the underside of said hood roof and then over the gap along the underside of said roof witha connection end to the front of the gap, the portion ofthe rear terminal extending over the gap comprising a pair .of spaced conductive ribs; a first spring seat on the underside of said hood that is positioned between said conductive ribs; a movable contact carrier with a second spring seat spaced beneath the first spring seat; a movable bridging contact carried by said carrier spanning said gap that is movable into and away from engagement with the contact ends of said front and rear terminals, said bridging contact being disposable above the contact ends of said terminals and also being disposable beneath the contact ends of said terminals; and a bias spring having one end resting against the side of said bridging contact facing away from the terminal contact ends to urge the bridging contact toward engagement with the contact ends of said terminals, said bias spring being seated against said first spring seat when said bridging contact is disposed above said contact ends and being seated against the second spring seat when said bridging contact is disposed below said contact ends.

5. In an electrical switch the combination comprising a front terminal with a connection end and a contact end to the rear thereof; a rear terminal having a contact end spaced to the rear of the contact end of the front terminal to present a gap therebetween, and turning upwardly and then over the gap with a connection end to the front of the gap, the portion of the rear terminal extending over the gap comprising a pair of spaced conductive ribs; a first spring seat positioned between said ribs; a movable contact carrier having a set of four guide rails extending normal to the contact ends of said terminals which are spaced to define the corners of a quadrilateral when viewed from above, and said contact carrier having a second spring seat spaced beneath said first spring seat; a movable bridging contact spanning said gap that is movable into and away from engagement with the contact ends of said front and rear terminals, said bridging contact extending between the guide rails of said carrier to limit sideward movement and to guide travel toward and away from said terminal contact ends, said bridging contact also being disposable both above the contact ends of said terminals and beneath the contact ends of said terminals; and a bias spring urging said bridging contact toward engagement with the contact ends of said terminals, which bias spring is seated against said first spring seat when said bridging contact is disposed above said contact ends and is seated against said second spring seat when said bridging contact is disposed below said contact ends.

6. In an electrical switch the combination comprising a front terminal with a connection end and a contact end; a rear terminal having a connection end and a contact end spaced from the contact end of said front terminal; a movable contact carrier having two pairs of guide rails with the pairs being spaced from one another and the rails of a pair being spaced, said carrier having a pair of transverse stops each stop extending between the rails of a pair at a point intermediate the ends of the pairs; a movable bridging contact movable toward and away from engagement with the terminal contact ends that extend between the two pairs of guide rails and having side extensions that each fit between the rails of a pair, said bridging contact being engageable by said stops to limit the travel thereof with respect to the carrier, and being disposable below the contact ends of said terminals in which event, the bridging contact is beneath said stops and disposable above said contact ends of said terminals in which event, the bridging contact is above said stops; and

10 a contact bias spring urging the bridging contact toward the terminal contact ends.

7. In an electrical switch the combination comprising a contact hood open at the bottom and having sides, a back, a front and a top; a front terminal supported by said contact hood with a connection end outside and to the front of the hood, and a contact end within the hood; a rear terminal supported by said contact hood with a contact end within the hood that is spaced rearwardly of the contact end of the front terminal to present a gap therebetween, which rear terminal turns upwardly from the contact end and then forwardly along the underside of the hood top in two separated ribs; and hence through the hood to present a connection end toward the front of the hood; a spring seat within the hood that is straddled by said separated ribs; a movable contact carrier that is movable substantially normal to the gap between the contact ends of said terminals that has a set of vertically extending guide rails with a cross member extending horizontal of the rails at a position between the upper and lower ends of the rails, which contact carrier presents a spring seat beneath the spring seat of said hood; a movable bridging contact spanning said gap between the contact ends of said terminals in bearing engagement with said guide rails for guided movement into and away from engagement with said contact ends, said bridging contact being disposable above the contact ends of said terminals in which position it is above said horizontal cross member to be struck thereby and carried above said contact ends and also being disposable beneath said contact ends of said terminals in which position it is below said horizontal cross member to be struck thereby and carried beneath said contact ends; and a bias spring urging said bridging contact toward engagement with said contact ends of said terminals, which spring is disposed with one end bearing against said spring seat of said hood when the bridging contact is above said contact ends and is disposed with one end bearing against the spring seat of said movable contact carrier when said bridging contact is beneath said contact ends.

8. In an electrical switch the combination comprising a contact hood having a plurality of contact receiving compartments each compartment being open at the bottom and having sides, back, front and top walls; a front terminal supported in each compartment with a connection end outside and to the front of the hood, and a contact end within the respective compartment; a rear terminal supported in each compartment with a contact end within the respective compartment that is spaced rearwardly of the contact end of the front terminal to present a gap therebetween, which rear terminal turns upwardly from the contact end and then forwardly along the underside of the compartment top in two separated ribs; and hence through the compartment wall to present a connection end toward the front of the hood; a spring seat within each compartment that is straddled by the separated ribs of the associated rear terminal; a movable contact carrier for each compartment movable substantially normal to the gap between the contact ends of the associated terminals that has a set of vertically extending guide rail means with a cross member extending horizontal of the rails at a position between the upper and lower ends of the rails, which contact carrier presents a spring seat beneath the spring seat of the compartment; a movable bridging contact for each contact carrier spanning the gap between the contact ends of the associated terminals in bearing engagement with the guide rail means of the carrier for guided movement into and away from engagement with the terminal contact ends, said bridging contact being disposable above the terminal contact ends in which position it is above said horizontal cross member to be struck thereby and carried above said contact ends and also being disposable beneath said terminal contact ends in which position it is below said horizontal cross member to be struck thereby and carried beneath said contact 11 ends; and a bias spring for each movable bridging con tact urging the associated bridging contact toward engagement with said terminal contact ends, which spring is disposed with one end bearing against the spring seat of the associated compartment when its associated bridging contact is above the terminal contact ends and which is disposed with one end bearing against the spring seat of the associated movable contact carrier when its associated bridging contact is beneath the terminal contact ends,

9. An electrical switch as in claim 8 having, in combination therewith, an electromagnetic actuator with a movable member supporting said movable contact carriers which extends and forms the sides of the actuator; a stationary contact receiving compartment mounted to the side of said actuator; a bracket mounted on the side of said actuator beneath the compartment; a movable contact carrier on said bracket; and front and rear terminals supported within said compartment.

10. In a contact structure the combination comprising a pair of stationary contact members spaced from one another; a movable contact carrier having guide rail means extending parallel to the line of motion of the movable carrier, said carrier having transversely extending stop means at a point intermediate the ends of the rail means; a movable bridging contact movable toward and away from engagement with said stationary contact members which is in sliding guided relation to said guide rail means, said bridging contact being disposable above said stationary contact members and said stop means, and being disposable beneath said stationary contact members and said stop means; and a bias spring associated with said movable contact which is disposed above the movable contact when the same is above said stationary contact members, and which is disposed below the movable contact when the same is below said stationary contact members.

References Cited in the file of this patent UNITED STATES PATENTS 1,853,964 Dorgeloh et al. Apr. 12, 1932 2,064,632 Schmitt Dec. 15, 1936 2,101,288 Van Valkenburg Dec. 7, 1937 2,106,581 Unwin Jan. 25, 1938 2,239,031 Bierenfeld et a1 Apr. 22, 1941 2,276,698 Pierce Mar. 17, 1942 2,343,323 Pierce Mar. 7, 1944 2,532,305 Heller Dec. 5, 1950 2,712,580 Nickell et al. July 5, 1955 2,758,169 Weide Aug. 7, 1956 2,773,948 Pelz et al Dec. 11, 1956 

